1. Field of the Invention
The present invention relates to a multi-cell coordinated communication technology in a wireless communication system, and more particularly to a pre-coding method, a pre-decoding method, a transmitter and a mobile terminal in the multi-cell coordinated communication system using an interference alignment scheme.
2. Description of the Prior Art
In a wireless mobile cellular network, if neighboring cells work at the same frequency range, user terminals at the border of a cell will be strongly interfered by the neighboring cells. This kind of interference is called co-channel interference. This kind of co-channel interference may influence the communication quality, such as the transmission data-rate and reliability, of user terminals at the border of the cell.
In the solution of a traditional communication system such as Global System for Mobile Communication (GSM), a frequency-division multiplexing is adopted, i.e. neighboring cells use different sub-bands for transmission. Thus, the interference between neighboring cells may be avoided. However, resources for transmitting useful signals are reduced and therefore frequency spectrum utilization efficiency is reduced. For example, according to new cellular system such as Long Term Evolution (LTE) network, different cells in the entire network or in part of the network all work at a same frequency band while the interference is suppressed by a co-channel interference management method so as to improve the communication quality.
Recently, interference alignment methods have been proposed. According to this method, not only the interference between cells is suppressed, but also more resources are reserved for transmitting useful signals. Based on these advantages, a more spectrum-efficient wireless transmission may be obtained by using the interference alignment method. A basic idea of the interference alignment is to divide a signal space into a desired signal sub-space and an interference signal sub-space and then to have all interference signals into the interference signal sub-space so as to effectively suppress the interference between cells.
Non-patent document 1 (C. Suh et. al., “Downlink Interference Alignment” GlobeCOM 2010) and Non-patent document 2 (W. Shin et. al. “On the Design of Interference Alignment Scheme for Two-Cell MIMO Interfering Broadcast Channels” IEEE Trans. on Wireless Comm. 2011) propose two multi-cell multi-user linear pre-coding and pre-decoding methods based on the interference alignment. However, researches on the interference alignment are focused on theoretical phase and not in practice.